Speed and electrical force responsive hydraulic governor units



April 24, 1962 .J. BAXTER ETAL 3,030,931 SPEED AND ELECTRICAL FORCE RESPONSIVE HYDRAULIC GOVERNOR UNITS Filed May 2'7, 1960 Fe'Ql/E/VC Y a Zona emu/a5 sews/Me Oeca/mr [Nd/IVE aver/Ame Q J v J 6 5 INVENTORS Q J. BAXTEB RC. HUNG'EEFOED TE. BY

tates The present invention relates to and provides a novel hydraulic governor unit wherein an engine speed sensitive mechanical-hydraulic governor mechanism and an electrical load and/or frequency sensitive, speed-changeanticipating governor mechanism are arranged for selectively exclusive control of engine speed interchangeably through operation of a single hydraulic servomotor which is common to the two mechanisms.

One object hereof is to provide such a governor unit wherein portions of the hydraulic circuits controlled by each mechanism are automatically and effectually isolated from connection with the servomotor whenever the other mechanism is conditioned for engine speed control operation.

Another object is to provide a novel mechanically and electrically operated transfer valve system is an isochronous hydraulic governor unit arranged for speed sensitive and electrical load and/or frequency sensitive control of engine speed through a common hydraulic servomotor, and whereby an engine/generator systemserved by the unit is automatic-ally and adequately safeguarded in event of electrical power failure.

If either governor servomotor control mechanism in a unit such as just above referred to has a hydraulic compensation system operated as a function of servomotor movement during speed corrections temporarily to change the pressure in a nearly closed compensation fluid passage and connected pressure chambers, then while the other governor mechanism is in control of speed it is undesirable for fluid in the compensation passage and chambers of such first mentioned governor mechanism to impose restraint on free movement of the servomotor. In the present arrangement as illustrated, indicating another object, when the electrically sensitive governor mechanism is activated the generally closed compensation fluid passage and connected chambers of the speed sensitive governor mechanism are automatically vented freely to governor sump.

The accompanying drawing is a schematic view of the governor unit hereof conditioned for speed control operation through electrically responsive means, the view further showing in block diagram suitable or typical electrical circuitry of a type adapted to be electrical load change and frequency sensitive.

The governor unit hereof as shown has a portion G (left) containing the principal components of a mechanical-hydraulic isochronous governor arranged generally in accordance with the disclosure of L. I. Moulton ct al., Patent 3,011,352, issued December 5, 1961, entitled Hydraulic Governor, and a portion E which is electrically controlled and which includes an electrically operated transfer valve unit or mechanism T. The movable member of valve mechanism T is a valve plunger 15 (hereinafter usually transfer valve 15) shown as being held in raised position electromagnetically as by a solenoid coil 17. During mechanical-hydraulic governing the transfer valve is held in the broken-line-illustrated (lowered) position of it by a spring 16 suitably connected to the valve plunger 15.

The electrically responsive mechanism or portion E, in addition to the transfer valve mechanism T, includes,

as shown, a control or pilot valve unit EP whose movable valve member (valve plunger 20, hereinafter usually valve 20) operates, through variable energization of an actuator coil 25, exclusively to control servomotor operation as will be more fully described later. The mechanical-hydraulic speed control system G is customarily conditioned for exclusive operation to control engine speed at commencement of engine operation and until all the electrical apparatus is in properly operating condition. The electrical load change and frequency sensing mechanism E including valve 20 is then rendered operative and remains in full control of engine speed. In event of emergency such as critical electrical power failure, fail-safe standby operation of the mechanicalhydraulic governer portion of the unit is initiated automaticallythe transition requiring only deenergization of transfer valve coil 17 as is more or less evident from the drawing.

The mechanical hydraulic governor G as shown has flyballs 1, a settable speeder spring 2, a pilot valve including valve plunger 3 (hereinafter pilot valve 3) and a differential type servomotor or governor output power piston mechanism 5 having differential pressure operated pistons 5a and 5b connected to a governor terminal rock shaft 6 for operation of the engine throttle or fuel rack not shown. Substantially constant supply pressure source P is adapted to be connected via transfer valve sleeve or bore 7 (transfer valve 15 then lowered) to a passage 4 leading into the sleeve of pilot valve 3. The chamber of piston 51; is continuously supplied with constant pressure oil through a passage P5. Movement of pilot valve land 3' out of its illustrated steady-state position (valve 15 still lowered) admits or exhausts servo piston cone trol pressure oil via passages 8 and 9 to or from the control chamber 9 of piston 5a. During steady-state (either mechanical or electrical sensing operation) operating oil is trapped in the servomotor control chamber 9' as by the main governor pilot valve land 3' or a land 20a of the valve 20 of unit EP. The various ports and openings marked S are connected to sump.

The mechanical-hydraulic governor mechanism G has a hydraulic compensation system of generally known type including as shown a chamber or passage C, an actuator pump C connected to power piston mechanism 5, a compensation pressure receiving piston C2 shown as formed by one end of pilot valve plunger 3, a yieldably positioned proportioner piston C3 and an adjustable leak-off valve C4, all serving their usual purpose of damping o s,- cillating action of the speed sensing governor mechanism during speed changes. During mechanical-hydraulic governing a lower land 15a of the transfer valve 15 (valve then in lowered position) closes the passage C to render the hydraulic compensation system active, and during governing by the electrical load or frequency sensing portion E of the present unit (full line showing of valve 15) the compensation passage C is vented automatically to sump so that oil which would otherwise be approximately trapped in the passage C will not restrain free movement of the power piston mechanism 5.

During equilibrium or steady-state operation under electrical control, valving land 20a of valve 20 blocks a passage 30 connected via the transfer valve sleeve 7 with the power piston control chamber 9' via passage 9 for control operation of governor servo piston mechanism 5 as a function of movement of valve 20 either up or down. Constant pressure oil is supplied to the sleeve 21 of valve 20 through a passage 26 which during mechanical governing is closed by a valve land 15c of the transfer valve 15 and which during electrical governing is communicated with supply passage P as a function of electrical energy being supplied to the coil 17 of the transfer valve mechanism T. Energy in the coil 17 acts on armature 17a to lift and maintain the transfer valve in the position of it shown in full lines against the opposing action of the return spring 16.

As will be evident from the drawing the transfer valve lands 15a and 15!; during electrically responsive governing block the passages 8 and 4 leading to the mechanicalhydraulic pilot valve chambers, thereby inactivating the flyweight mechanism 1, 2 and pilot valve 3 by isolating the valve chambers of the latter from the pressure supply source P and from the control chamber of power piston 5a.

During electrical-hydraulic control operation of the present unit the valve is maintained in equilibrium position by opposed forces including those of a speed function reference spring 22 and a feedback spring 23 in series therewith operatingly connected to the valve 20 and to the governor terminal shaft 6 through linkage including a pivoted armature 24 disposed to be acted upon magnetically by actuator solenoid coil 25 in a direction to initiate fuel reducing movement of terminal shaft 6. The reference spring '22 is shown interposed between a fixed support 22a and a shoulder 22b on valve 20. When the engine 36 is operating at rated or desired normal speed and full load, the combined forces of springs 22 and 23 in effect exactly balance the magnetic force of actuator coil 25 on armature 24 pursuant to the coil 25 being supplied by current at the desired value for normal or rated load operation of the engine and reference frequency of generator 35.

The feedback spring 23 operates through armature 24 on valve 20 as a function of movement of terminal shaft 6 to tend to restore the valve 20' to neutral position or in a manner to stabilize the mechanism during transients, i.e., similarly to the action of the hydraulic compensation system C, C, etc. One way in which the feedback operation of spring 23 can be prevented from producing permanent speed change varying with load (permanent droop) is to design the springs 23 and 22 so that their net force variation in a desired range exactly matches the rate at which the current, hence magnetic force of control coil 25 increases with diminished electrical load and vice versa. Stabilization during transients can be attained via the circuitry 38 by automatic adjustment of its elements to provide the necessary reset rate control and feedback.

Electrical load change and frequency sensing coil 25 may be variably energized in various ways as a function of output of the generator indicated in the drawing as a three phase alternator driven by the engine 36 whose speed is controlled by the governor unit hereof. The circuitry 38 may be of a known type such that current in the coil 25 is increased as a function either of decreased electrical load or of increase in the output frequency of the generator. One example of a suitable type of control apparatus is being sold by Electric Regulator under the trade name or mark Govohm. During occurrence of electrical transients (e.g., decrease in electrical load) and without waiting for the engine speed or frequency to change, the valve 20 is moved downwardly, spilling trapped oil from the control chamber of power piston and causing engine-fuel-decreasing (clockwise) movement of terminal shaft 6 or in other words performance of the same engine fuel controlling operation as would have been performed by the governor mechanism G, had it been conditioned for operation, but faster. Decrease in current in the control coil 25 or decrease in generator output frequency effects the reverse of the above described operation the valve 20 being moved upward-1y as by reference spring 22 to initiate fuel increasing movement of the terminal shaft 6 and slacking of feedback spring 23.

It is sometimes desirable temporarily to restore control of the engine to the mechanical-hydraulic governor mechanism G while the electrical load and frequency sensing coil 25 remains energized. The operating coil 17 of the transfer valve 15 can in suchcase be manually deenergized and reenergized by operation of a suitable switch 39 connected to coil 17 and which is preferably of the magnetically locked in type (holding circuit not shown) for fail-safe operation as already mentioned and so that, after switching from electrical to mechanical-hydraulic governing any return to electrical governing after power failure has occurred will require an act of an attendant. The coil 17 can alternatively or additionally be automatically deenergized by a switch contact (not shown) in the electrical load and frequency response circuitry 38 set for predetermined high and low frequency limits.

We claim:

1. A hydraulic speed governor unit comprising a single hydraulic servomotor having a control chamber, a speed responsive pilot valve mechanism including passage means connected to said chamber to control operation of the servomotor, an electrical force sensitive pilot valve mechanism including other passage means connected to the chamber for operation of the servomotor, an operating fluid source, and a transfer valve including passage means interconnecting the source and the passage means of each pilot valve mechanism, said transfer valve having two positions, the transfer valve in one position thereof connecting the fluid pressure source to the control chamber of the servomotor exclusively through the speed responsive pilot valve mechanism and in the other position thereof connecting the source to the control chamber exclusively through the electrical force sensitive pilot valve mechanism.

2. The governor unit according to claim 1, including electromagnetic means operatingly connected to the transfer valve and operable to move it in a direction toward said other position against a constantly acting return force such as that of a spring.

3. The governor unit according to claim 2, including an electric circuit connected to supply electrical energy to said electromagnetic means, a switch in the circuit adapted to be closed for initiating operation of the electromagnetic means, and means connected in the circuit and operative to open the switch in event of predetermined deviation of energy in the circuit from a desired value.

4. A governor unit according to claim 1, wherein one pilot valve mechanism has a generally closed hydraulic compensation dashpot system acting thereon as a function of servomotor movement to render the governor unit isochronous, and a compensation fluid system dump valve connected for operation into open position by the transfer valve when the latter is in position to connect the other pilot valve mechanism to the control chamber of the servomotor and for operation into closed position when the transfer valve is in position to connect said one pilot valve mechanism to the control chamber.

5. A hydraulic governor unit comprising a single hydraulic servomotor having a control chamber, a fluid pressure source for operation of the servomotor, a speed responsive pilot valve mechanism including passage means between it and the control chamber controllably to connect the source to the control chamber, a first electrical force responsive means and a second pilot valve mechanism operated thereby and including passage means enabling connection of the source controllably to the control chamber, a transfer valve connected to both passage means and movable into two positions selectively to condition the pilot valve mechanisms for exclusive control of the servomotor at different times, a spring constantly tending to hold the transfer valve in one position wherein it is operative to condition the speed responsive pilot valve mechanism for control of the servomotor, and a second electrical force responsive means electrically connected to be energized concurrently with energization of the first electrical force responsive means to hold the transfer valve in its other position.

6-. In a governor unit according to claim 5, a hydraulic compensation system including a generally closed compensation fluid passage having a leak-off orifice comr 5 municating the compensation fluid passage to sump, an actuator pump connected to the servomotor for operation thereby to change pressure in the compensation fluid passage, and a pressure operated device exposed to pres sure in the compensation fluid passage and connected for temporary speed resetting action on the speed responsive pilot valve mechanism, a port adapted for unrestricted communication of the generally closed passage with the sump, and a valve device connected for operation by the References Cited in the file of this patent UNITED STATES PATENTS Burritt July 17, 1951 Whitehead et a1. Aug. 4, 1953 Sweet Feb. 9, 1954 

